This invention relates to the production of electric motors, and in particular, to a gage for use in measuring the extension of the motor's rotor shaft beyond an end shield of the motor.
Electric motors conventionally include a stator assembly and a rotor assembly contained within a shell. The shell is commonly closed by at least one end shield. The rotor assembly includes a rotor and a shaft. The shaft is journaled for rotation along bearings commonly positioned in the end shield. The rotor shaft extends from at least one end of the motor. The shaft extension is installed in, and drives, an original equipment manufacturer's (OEM's) product, such as a fan or pump. For the motor to fit in the manufacturer's product properly, the rotor shaft extension from the motor must lie within certain predetermined tolerance limits. As will be appreciated by those skilled in the art, the rotor shaft mounted in the end shield will have a certain amount of axial tolerance, commonly referred to as axial end play. The overall shaft extension and end play must be within the tolerance limits set by the OEM.
Presently, shaft extension is measured after the motor construction is essentially completed. If the shaft extension is too long or too short, the motor must be disassembled so that shims can be inserted or removed to correct the extension length, and then reassembled. If the shaft extension is still not correct, the process must be repeated. This is a labor intensive and time consuming process and adds time and expense to the production of an electric motor.
Presently, the rotor shaft end play also is manually measured after the motor manufacture is essentially completed. If the end play is not within the predetermined limits, one of the endshields must be removed so that end play shims can be added or removed to correct the end play. When the motor is reassembled, end play is measured again. If it is still not correct, the procedure must again be repeated. The need to disassemble the motor to correct end play, and then reassembly the motor is both time consuming, and hence expensive, and tedious. Further, because the end play is manually determined, the measurement is subject to human error. Because the end play and shaft extension are interrelated, the process requires several corrections. That is to say, end play tolerance, or a lack thereof, affects shaft extension tolerances. As will be appreciated by those skilled in the art, even if shaft extension is not an issue, proper end play can affect motor performance, operating characteristics, and operational life.
Shaft size or diameter also can cause problems in applicational use. As indicated above, the shaft converts electrical input to the motor to useful mechanical work. The conversion is accomplished by attaching the motor shaft to another device. If shaft size prevents that attachment, the motor is useless for its intended application.